[FFmpeg-devel] [PATCH] avutil/mathematics: speed up av_gcd by using Stein's binary GCD algorithm

Henrik Gramner henrik at gramner.com
Sat Oct 10 23:32:06 CEST 2015

On Sat, Oct 10, 2015 at 11:06 PM, Ganesh Ajjanagadde
<gajjanagadde at gmail.com> wrote:
> This uses Stein's binary GCD algorithm:
> https://en.wikipedia.org/wiki/Binary_GCD_algorithm
> to get a reported 1.7-2.1x speedup over Euclidean GCD on standard architectures.
> Have not benchmarked, so I can't comment

Before you submit a patch that's supposed to make something faster,
you should benchmark it to verify that it is in fact faster. Do this
with inputs of various sizes on both 32- and 64-bit architectures and
both with and without compilers that support __builtin_ctzll(v).

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